Developmental Exposure to Perchlorate Alters Synaptic Transmission in Hippocampus of the Adult Rat

These findings indicate that neurologic impairment is associated with modest degrees of thyroid hormone insufficiency and support previous animal studies of neurodevelopmental sequelae associated with low levels of perchlorate exposure

Mary E. Gilbert; Li Sui

2008

Scholarcy highlights

  • Perchlorate is an environmental contaminant that blocks iodine uptake into the thyroid gland and reduces thyroid hormones
  • Dose-dependent deficits in hippocampal synaptic function were detectable with relatively minor perturbations of the thyroid axis, indicative of an irreversible impairment in synaptic transmission in response to developmental exposure to perchlorate
  • Recent reports indicate that children born to women experiencing modest subclinical perturbations of the thyroid axis during pregnancy have reduced IQ scores and subtle deficits in cognition, memory, and visuospatial ability and a higher incidence of attention deficit hyperactivity disorder
  • Perchlorate induced a disruption of hormonal status in the neonate that recovered upon termination of exposure, yet a pronounced deficit in neurophysiologic properties of the hippocampus was evident in adulthood. These findings indicate that neurologic impairment is associated with modest degrees of thyroid hormone insufficiency and support previous animal studies of neurodevelopmental sequelae associated with low levels of perchlorate exposure
  • Hypothyroxenemia induced in dams and pups by developmental exposure to perchlorate was associated with deficits in excitatory and inhibitory synaptic function in the hippocampus
  • A modest but significant reduction in T4 was seen in PND21 pups in the 300and 1,000-ppm dose groups
  • Recent reports from the Centers for Disease Control and Prevention demonstrating a strong association between perchlorate exposure and serum levels of thyroid hormone in women with marginal iodine deficiencies raise considerable public concern about the impact of this contaminant on the developing fetus
  • The present data provide evidence in a rodent model that modest degrees of thyroid hormone reduction induced by perchlorate result in persistent decrements in brain function

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